The generic paint spray gun is known from EP 0 706 832 B1. Said paint spray gun presents a compressed air distributor which is connected to a compressed air feed line, and which distributes the compressed air of the compressed air feed line over a horn air supply line and a round jet supply line. The compressed air quantity fed to the horn air supply line can be set by screw adjustment of a plug, which presents a terminal sealing spigot for continuous opening or closing of the horn air supply line. To delimit the pressure that is generated in the round jet area to a maximum, if at the time of the closing of the horn air the pressure in the round jet area increases above the maximum admissible for paint spray guns, the plug presents, seen from its end, an area of larger diameter, in the direction towards the sealing spigot, which also continuously narrows the air pathway between the compressed air feed line and round jet supply line, at the time of the closing of the horn air supply line. The plug is shifted there by means of a knurled knob rotating in the axial direction. The solution described therein presents the disadvantage that, owing to the axial resetting kinematics of the plug for opening or closing the lines in the compressed air distributor, the knurled knob needs to be turned one rotation. Moreover, the design of the plug with the sealing spigots and the plate-like disk makes it impossible to determine or calculate with precision the distribution of air in the compressed air distributor. In addition, the multipart design is disadvantageous here from the point of view of manufacturing technology. Moreover, during the adjustment, the distance between the knurled knob and the gun body changes, which is often perceived as disadvantageous.